Serum inhibin B in combination with serum follicle-stimulating hormone (FSH) is a more sensitive marker than serum FSH alone for impaired spermatogenesis in men, but cannot predict the presence of sperm in testicular tissue samples.

The measurement of serum FSH is useful in the diagnostic workup of the infertile male, but fails to predict the presence of sperm in testicular tissue. We investigated whether inhibin B reflects testicular morphology and the presence of sperm more accurately than FSH. Serum inhibin B and gonadotropin levels were determined in 91 infertile men undergoing diagnostic bilateral testicular biopsy. In 52 of the 91 patients multiple samples were taken for testicular sperm extraction (TESE). Inhibin B levels were (mean +/- SEM) 238+/-32 pg/mL in men with normal spermatogenesis (n = 9), 102+/-18 pg/mL in men with spermatogenetic arrest (n = 15), 98+/-16 pg/mL in hypospermatogenesis (n = 23), 41+/-6 pg/mL in focal Sertoli cell-only syndrome (SCO; n = 26), and 27+/-8 pg/mL in complete SCO (n = 18). The percentage of SCO tubuli was more strongly correlated to serum inhibin B (r = -0.58; P<0.01) than to FSH (r = 0.34; P<0.05). Similarly, the percentage of tubules with elongated spermatids was significantly (P<0.05) more strongly correlated to serum inhibin B (r = 0.65; P<0.01) than to FSH (r = -0.4; P<0.01). Thus, inhibin B is slightly more sensitive than FSH as an index of the spermatogenic status. Neither FSH nor inhibin B alone, however, could predict the type of spermatogenetic damage exactly. The combination of FSH and inhibin B had high diagnostic sensitivity (88%) and specificity (83%) for the presence of elongated spermatids in testicular biopsies. Sperm could be retrieved in 34 (65%) of the TESE patients. The combination of inhibin B and FSH measurement showed a sensitivity of 75% and a specificity of 73% when identifying patients in whom sperm could possibly be retrieved by TESE. We conclude that although the measurement of serum inhibin B improves the sensitivity of predictive tests for the presence of sperm in histology or for TESE, this parameter cannot accurately predict TESE outcome.     

Serum inhibin B levels in community-dwelling elderly men

BACKGROUND: AND OBJECTIVE: Ageing in men is accompanied by a decline of Leydig cell function, with a 50% decrease of the population means for serum free testosterone between age 25 and 75 years. Information on Sertoli cell function and spermatogenesis in the elderly is scarce. Studies on seminal parameters in ageing men have suggested that spermatogenesis may be fairly well maintained in the elderly, but they included mostly selected subjects and only few men over 60 years. More systematic studies are lacking. The aim of the present study was to assess serum inhibin B levels in elderly men as an index of global Sertoli cell function and spermatogenic activity. SUBJECTS AND MEASUREMENTS: Specific immunoassays were used to determine serum levels of inhibin B, gonadotrophins, testosterone and oestradiol in blood obtained between 0800 and 1000 h. from 189 ambulatory, community-dwelling elderly men (age: 70-85 years) and, for comparison, from 51 middle-aged (35-54 years) and 50 young (< 35 years) controls. RESULTS: All age groups combined, serum inhibin B was only weakly negatively correlated to age (Spearman correlation coefficient: - 0.17; P < 0.01) and more strongly to serum FSH (- 0. 52; P < 0.001). In a multiple regression analysis serum FSH, but not age or serum free testosterone, emerged as an independent determinant of serum inhibin B levels. An age-related decline of median inhibin B levels in the study population was essentially limited to the younger age groups, with stable levels between age 35 and 79 years, and only a modest further decrease thereafter. There was a progressive age-related increase of serum FSH across age groups with, consequently, a marked decrease of the serum inhibin B : FSH ratio. The prevalence of men presenting with low serum inhibin B (below 10th percentile for inhibin B levels in men < 35 years), indicative of deficient Sertoli cell function and spermatogenesis, increased most strikingly between men < 35 years and those 35-54 years, which contrasts with the more progressive increase at an older age of the prevalence of low serum (free) testosterone. CONCLUSION: Global testicular Sertoli cell function and spermatogenic activity, as assessed indirectly through serum inhibin B levels, appear to be well maintained in ambulatory elderly men, albeit there are age-related alterations at the level of the Sertoli cells as indicated by a progressive increase of testicular drive by pituitary FSH.     

Treatment of gonadotropin-deficient boys with recombinant human FSH: long-term observation and outcome

BACKGROUND: Boys with prepubertal onset of hypogonadotropic hypogonadism (HH) are at a risk of poor testis growth and impaired spermatogenesis. One potential cause for this is deficient proliferation of immature Sertoli cells before and during puberty due to the absence of FSH. OBJECTIVE: To evaluate the effects of recombinant human FSH (r-hFSH) and human chorionicgonadotropin (hCG) on testicular function and pubertal development in boys with prepubertal onset of HH. DESIGN: Retrospective clinical study. SETTING: Two university central hospitals, pediatric referral endocrinology outpatient clinics. PATIENTS: Fourteen boys (aged, 9.9-17.7 years) with prepubertal (testicular volume (TV) <3 ml) onset of HH (idiopathic HH, n=2; Kallman syndrome, n=2; idiopathic panhypopituitarism, n=4; organic panhypopituitarism, n=6). INTERVENTION: Treatment with r-hFSH alone (2 mo-2.8 years) prior to induction of puberty with the combination of FSH and hCG. Main outcome measures: Progression of puberty, change in serum inhibin B, spermatogenesis. RESULTS: r-hFSH alone increased testicular volume twofold, from 0.9+/-0.6 ml (mean+/-s.d.) to 1.8 +/- 1.1 ml (P<0.005), and serum inhibin B threefold, from 27+/-14 to 80+/-57 pg/ml (P<0.01). Three boys with an apparent absence of postnatal hypothalamic-pituitary-testicular axis activation displayed attenuated inhibin B responses to long-term (>or=1 year) r-hFSH (P<0.01). Further significant increase in both TVand inhibin B occurred with induction of puberty with FSH and hCG (P<0.001). Seven boys provided semen samples: one had azoospermia, and others displayed a maximal sperm count range from 2.9 to 92 million/ml (median 8.5 million/ml). CONCLUSIONS: (i) r-hFSH induces prepubertal testis growth and increases circulating inhibin B levels, findings suggesting proliferation of immature Sertoli cells. (ii) Puberty was successfully induced with hCG and r-hFSH following r-hFSH priming. (iii) Inhibin B appears useful for monitoring spermatogenetic activity in boys treated with hCG. (iv) Despite the extremely small initial testis volume, six out of seven patients (86%) primed with r-hFSH displayed sperm in the ejaculate suggesting beneficial effect of r-hFSH priming on testicular function later in life.     

Relationship of serum inhibin levels to serum follicle stimulating hormone and sperm production in normal men and men with varicoceles.

The purpose of this study was to examine the relationships between serum inhibin levels as measured by RIA and serum FSH and sperm concentration. Three groups of men were used for this study: group I, normal fertile men (n = 67); group II, fertile men with a varicocele (n = 57); and group III, infertile men with a varicocele (n = 21). There were no differences in mean serum inhibin levels between the three groups. The two groups of men with varicoceles exhibited higher serum FSH levels and FSH responses to GnRH than the normal men. Sperm counts in both groups II and III were significantly lower than group I. In the normal men there was an inverse correlation between baseline serum inhibin and serum FSH levels and GnRH stimulated FSH levels, r = -0.415 and 0.422, P less than 0.005, respectively. Furthermore, the normal men exhibited a positive correlation between serum inhibin measurements and sperm concentration and testicular volume, r = 0.35 and 0.26, P less than 0.01 and less than 0.05, respectively. In neither group of men with a varicocele were these relationships found. These data demonstrate that serum inhibin does correlate with FSH in a negative fashion, when the reproductive system is normal, as would be expected for a negative feedback factor. Finally, the relationship of serum inhibin levels to testicular size and sperm count in the normal men suggests that serum inhibin levels reflect to some extent the integrity of seminiferous tubule function.     

Effects of human recombinant luteinizing hormone and follicle-stimulating hormone in patients with acquired hypogonadotropic hypogonadism: study of Sertoli and Leydig cell secretions and interactions

Experimental data suggest that FSH-stimulated Sertoli cells can enhance LH-induced Leydig cell testosterone (T) production. The function of Leydig and Sertoli cells can be selectively studied by using recombinant human LH (rhLH) and recombinant human FSH (rhFSH) in patients with complete gonadotropin deficiency. The aim of the present study was to assess the secretion of testicular T, estradiol (E2), and inhibin B and the physiological relevance of the Sertoli-Leydig cell interaction in man. For that purpose, six patients with acquired complete hypogonadotropic hypogonadism received the following treatments for three periods of 1 month in a random order: 1) rhLH, 900 IU/day sc; 2) rhFSH, 150 IU/day sc; and 3) combined rhLH/rhFSH treatments. Each treatment period was separated by a washout period of 15 days. Plasma LH, FSH, T, E2, and inhibin B were measured before and every 10 days during each treatment. During rhLH administration, mean plasma LH levels rose significantly from 0.4 +/- 0.2 IU/L to 11.7 +/- 1.2 IU/L (P < 0.01) and plasma FSH levels did not change. rhFSH administration induced a significant increase in plasma FSH levels (from 0.5 +/- 0.4 to 12.1 +/- 1.4 IU/L; P < 0.01), whereas mean plasma LH levels remained low. Mean plasma E2 levels were unchanged during rhFSH treatment, but they increased significantly during rhLH from 22 +/- 4 to 54 +/- 8 pmol/L (P < 0.01) and during rhLH plus rhFSH administration. rhFSH treatment induced a sustained elevation of mean plasma inhibin B levels from 58 +/- 13 to 175 +/- 25 pg/mL (P < 0.01), similar to the increase occurring during rhFSH plus rhLH administration. In contrast, mean plasma inhibin B levels did not increase during rhLH administration. Finally, a similar and significant increase in mean plasma T levels occurred during both rhLH and rhLH plus rhFSH treatment from 0.9 +/- 0.3 to 5.4 +/- 0.7 nmol/L (P < 0.01) and from 1.0 +/- 0.4 to 6.0 +/- 0.9 nmol/L (P < 0.01), respectively. In contrast, during rhFSH treatment mean plasma T levels remained unchanged when compared with baseline. In conclusion: 1) the increase of plasma E2 induced by rhLH and the absence of effect of rhFSH confirm that Leydig cells are the major site of testicular E2 production in man; 2) the secretion of inhibin B is increased by rhFSH and not by rhLH, and, thus, Sertoli cells seem to be the main source of inhibin B production; and 3) the increase of plasma T induced by rhLH is not enhanced by rhFSH. These results suggest that the stimulatory effect of FSH on Leydig cell steroidogenesis by a Sertoli cell paracrine factor does not seem to play a major physiologic role in man.     

Inhibin B in male reproduction: pathophysiology and clinical relevance.

The recent availability of specific inhibin assays has demonstrated that inhibin B is the relevant circulating inhibin form in the human male. Inhibin B is a dimer of an alpha and a betaB subunit. It is produced exclusively by the testis, predominantly by the Sertoli cells in the prepubertal testis, while the site of production in the adult is still controversial. Inhibin B controls FSH secretion via a negative feedback mechanism. In the adult, inhibin B production depends both on FSH and on spermatogenic status, but it is not known in which way germ cells contribute to inhibin B production. The regulation of inhibin B production changes during life. There is an inhibin B peak in serum shortly after birth only partly correlated with an increase in serum FSH, probably reflecting the proliferating activity of the Sertoli cells during this phase of life. Afterwards, inhibin B levels decrease and remain low until puberty, when they rise again, first as a consequence of FSH stimulation and then as a result of the combined regulation by FSH and the ongoing spermatogenesis. In the adult, serum inhibin B shows a clear diurnal variation closely related to that of testosterone. The administration of FSH increases the secretion of inhibin B in normal men, but is much more pronounced in males with secondary hypogonadism. The treatment of infertile men with FSH, however, does not result in an unequivocal inhibin B increase. There is a clear inverse relationship between serum inhibin B and FSH in the adult. Serum inhibin B levels are strongly positively correlated with testicular volume and sperm counts. In infertile patients, inhibin B decreases and FSH increases. In general, there is very good correlation with the degree of spermatogenetic damage, with the arrest at the earlier stages having the lowest inhibin B levels. However, for unknown reasons, there are cases of Sertoli-cell-only syndrome with normal inhibin B levels. Inhibin B and FSH together are a more sensitive and specific marker for spermatogenesis than either one alone. However, the inhibin B concentrations are not a reliable predictor of the presence of sperm in biopsy samples for testicular sperm extraction. Suppression of spermatogenesis with testosterone and gestagens leads to a partial reduction of inhibin B in serum but it is never completely suppressed. In contrast, testicular irradiation in monkeys or humans leads to a rapid and dramatic decrease of inhibin B, which becomes undetectable when germ cells are completely absent. In summary, although inhibin B is a valuable index of spermatogenesis, the measurement of serum inhibin B levels is still of limited clinical relevance for individual patients.     

Decreased serum inhibin levels in normal elderly men: evidence for a decline in Sertoli cell function with aging

Compared to young men, normal elderly men have decreased sperm production despite elevated serum gonadotropin levels. To determine whether the seminiferous tubule defect in elderly men includes decreased Sertoli cell function, we measured serum immunoreactive inhibin concentrations in young and elderly men before and after clomiphene citrate (CC) administration. Thirty-eight healthy men, 19 young (aged 22-35 yr) and 19 elderly (aged 65-85 yr), were studied before CC administration. The mean baseline serum inhibin level was significantly lower (P less than 0.001) in the elderly men than in the young men [416 +/- 22 (+/- SE) vs. 588 +/- 30 U/L], while serum immunoreactive FSH and LH levels were higher in the older men, and bioactive FSH levels were similar in the two age groups. Eleven young men and 13 elderly men were studied after 1 week of CC administration. The mean serum inhibin level increased by 71%, from 566 +/- 36 to 970 +/- 82 U/L, in the young men, but it increased by only 24%, from 421 +/- 26 to 520 +/- 38 U/L, in the elderly men. Serum immunoreactive LH and bioactive and immunoreactive FSH concentrations increased to similar levels in both groups after CC administration. We conclude that the seminiferous tubule defect of elderly men includes decreased Sertoli cell function.     

Inhibin B in men with severe obesity and after weight reduction following gastroplasty

Although the effect of obesity on some gonadal functions in men is known, its effect on Sertoli cell function has not been reported. We tested the hypothesis that the serum inhibin B level is decreased in men with severe obesity, and that this change persists after significant weight loss. We measured gonadal hormones in 17 obese men before (baseline) and after weight reduction following silastic ring vertical gastroplasty (SRVG). Their baseline body mass index (BMI) was 44.3 +/- 1.7 kg/ m2, mean +/- standard error of the mean (SEM). Seven of 16 obese men (44%), compared to 8 of 69 reference men (12%), had a baseline inhibin B level below 100 pg/ml (p < 0.01). A weak inverse association was found between inhibin B and BMI before weight reduction (r = -0.494, p = 0.072). Furthermore, FSH levels, which were weakly inversely associated with inhibin B levels (r = -0.482, p = 0.059), were inappropriately unelevated in 5 of the 7 obese men with low (below 100 pg/ml) inhibin B. After a weight reduction of 40 +/- 2.6 kg, mean +/- SEM, following surgery, the obese men's BMI was 31.6 +/- 1.5 kg/m2, mean +/- SEM, and inhibin B normalized in 3 of the 7 patients with low inhibin B. Despite weight reduction, FSH remained inappropriately unelevated in 2 of the 4 patients whose inhibin B remained low. This study also confirmed previously published findings that obese men have low serum total and free testosterone and relative hypogonadotropic (low LH) hypogonadism that may persist after weight reduction. In conclusion, Serum inhibin B levels in obese men may be low. This may be due to relative hypogonadotropic (also low FSH) hypogonadism.     

Stimulation of serum inhibin concentrations by gonadotropin-releasing hormone in men with idiopathic hypogonadotropic hypogonadism

Inhibin is a gonadal hormone thought to be important in FSH regulation. We investigated the effects of the hypogonadotropic state and subsequent GnRH-induced increases in gonadotropin levels on inhibin secretion. Serum levels of inhibin, LH, FSH, and testosterone (T) as well as sperm concentrations were measured in 5 men with idiopathic hypogonadotropic hypogonadism (IHH) before (baseline) and during 8 weeks of GnRH therapy (5 micrograms, sc, every 2 h). Baseline and peak inhibin levels were compared to those in a group of 19 normal men. Before GnRH administration, the mean serum inhibin level was significantly lower in the IHH men than in the normal men [166 +/- 56 (+/- SE) vs. 588 +/- 30 U/L; P less than 0.001]. Serum inhibin levels rose after 1 week of GnRH therapy (P less than 0.05) and remained higher than the baseline level thereafter. The mean peak inhibin level during GnRH administration was lower than the mean value in normal men (485 +/- 166 vs. 588 +/- 30 U/L; P less than 0.05). Serum LH and FSH levels rose promptly to the midnormal range or slightly above it. Serum T levels did not significantly increase until 4-5 weeks of GnRH administration and remained in the low normal range. All IHH men were azoospermic throughout the study. These data are consistent with the hypothesis that inhibin is produced by the testis under gonadotropin control. They also suggest the possibility of defective Sertoli and Leydig cell function in men with IHH, since the men's serum inhibin and T levels did not rise to the same extent as did their normalized serum gonadotropin levels during GnRH administration.     

High normal testosterone levels in infants with non-mosaic Klinefelter's syndrome

OBJECTIVE: Klinefelter's syndrome (KS) is associated with hypergonadotrophic hypogonadism in adulthood. However, limited information exists about the age at which hypogonadism occurs. The hypothalamic-pituitary-gonadal (HPG) axis is transiently activated during the first months of life, offering the opportunity to study testicular function by spontaneous, basal hormone levels. The aim of this study was to evaluate the HPG axis in KS infants. DESIGN: Cross-sectional study. METHODS: Ten KS infants aged 3.1 months (range 1.8-3.8) and 613 healthy controls aged 3.0 months (range 2.0-4.5). Serum levels of total and free testosterone (T), LH, FSH, inhibin B and sex hormone-binding globulin (SHBG) were determined. RESULTS: KS infants had significantly higher concentrations of total T (5.0 (2.2-11.2) vs 3.4 (0.7-8.3) nmol/l, P = 0.02), free T (31.6 (18.2-61.8) vs 22.1 (4.3-48.4) pmol/l, P = 0.01), LH (3.3 (1.3-4.6) vs 1.7 (0.6-4.3) IU/l, P = 0.005) and FSH (1.7 (1.1-4.1) vs 1.2 (0.4-3.0) IU/l, P = 0.007) than controls. SHBG and inhibin B did not differ from controls. LH/T and LH/free T ratios were normal, whereas the FSH/inhibin B ratio was elevated (6.5 (2.7-16.9) vs 3.0 (0.78-11.4), P = 0.005) when compared to controls. The majority of KS infants had normal bivariate hormonal combinations. CONCLUSION: We found increased FSH/inhibin B ratio as a possible sign of Sertoli cell dysfunction. However, serum levels of T were high normal suggesting an altered pituitary-gonadal set point.     

Effects of testosterone plus medroxyprogesterone acetate on semen quality, reproductive hormones, and germ cell populations in normal young men

Testosterone (T) treatment suppresses gonadotropin levels and sperm counts in normal men, but the addition of a progestin may improve the efficacy of hormonal contraception. This study aimed to investigate the speed and extent of suppression of testicular germ cell number induced by T plus or minus progestin treatment and correlate these changes with serum gonadotropins and inhibin B levels, testicular androgens, and sperm output. Thirty normal fertile men (31-46 yr) received either testosterone enanthate (TE, 200 mg im weekly) alone or TE plus depot medroxyprogesterone acetate (DMPA, 300 mg im once) for 2, 6, or 12 wk (n = 5 per group) before vasectomy and testis biopsy. Five men (controls) proceeded directly to surgery. The inclusion of DMPA led to a more rapid fall in serum FSH/LH levels (time to 10% baseline: FSH; 12.6 +/- 2.6 vs. 7.9 +/- 1.4 d; LH, 9.9 +/- 3.4 vs. 3.4 +/- 1.7 d, TE vs. TE+DMPA, respectively, mean +/- SD, both P < 0.0001), yet the mean time to reach a sperm count 10% of baseline was not different (23.7 +/- 7.3 vs. 25.3 +/- 13.9 d, NS). The maximum extent of FSH/LH suppression was identical at 12 wk (mean serum FSH 1.2 and 1.6%, and mean LH 0.3 and 0.2% of baseline: TE vs. TE+ DMPA, respectively) as was sperm count suppression (5 of 5 and 4 of 5 men, respectively, with sperm counts < or =0.1 x 10(6)/ml). Serum inhibin decreased to 55% control at 12 wk in the TE+DMPA group (P < 0.05) but was unchanged by TE treatment (86% control, NS). Testicular T levels declined to approximately 2% of control levels, but testicular dihydrotestosterone and 5alpha-androstane-3alpha,17beta-diol (Adiol) levels were not different to control. Germ cell numbers as determined by stereological methods did not differ between TE and TE+DMPA except at 2 wk when type B spermatogonia and early spermatocytes were significantly lower in the TE+DMPA group (P < 0.05). In all groups, a marked inhibition of Apale-->B spermatogonial maturation was seen along with a striking inhibition of spermiation. We conclude that: 1) the addition of DMPA hastens the onset of FSH/LH suppression, correlating with a more rapid impairment of spermatogonial development, but in the longer term, neither germ cell number nor sperm count differed; 2) testicular dihydrotestosterone and Adiol levels are maintained during FSH/LH suppression despite markedly reduced T levels suggesting up-regulation of testicular 5alpha-reductase activity; and 3) spermatogonial inhibition is a consistent feature, but spermiation inhibition is also striking and is an important determinant of sperm output.     

Immunoreactive plasma inhibin levels in men after polyvalent chemotherapy of germinal cell cancer.

In vitro studies have shown that the Sertoli cell is the primary source of inhibin in the male. We measured immunoreactive inhibin with a new two-site immunoenzymatic assay in the plasma of 92 men: 40 normal men, 7 patients with germinal cell cancer after unilateral orchidectomy and 45 patients with the same disease following unilateral orchidectomy and subsequent chemotherapy based on cisplatin. Normal men had inhibin levels of 1.77 +/- 0.09 U/l x 10(-3) (mean +/- SEM). Seven patients after unilateral orchidectomy had inhibin concentrations within the lower normal range (1.23 +/- 0.22 U/l x 10(-3)). Forty-five patients were investigated in a cross-sectional study up to 102 months after completion of chemotherapy. Inhibin levels were within the normal range in 25 patients (1.76 +/- 0.14 U/l x 10(-3)); 18 patients had significantly lower inhibin levels (0.48 +/- 0.05 U/l x 10(-3), p less than 0.005) when compared to patients after unilateral orchidectomy. Two patients had elevated inhibin levels (4.4 and 5.6 U/l x 10(-3)). The proportion of patients with normal and subnormal inhibin was not dependent on the time that elapsed after completion of chemotherapy or on the chemotherapy combination. There was no correlation between immunoreactive plasma inhibin and LH, FSH, testosterone or sperm count. The decrease in inhibin concentrations after chemotherapy may indicate long-term damage to Sertoli cells in some of the patients.     

Changes in circulating and testicular levels of inhibin A and B and activin A during postnatal development in the rat

This study describes the testicular levels of inhibin/activin subunits by Northern analysis and in situ hybridization and serum and testicular levels of inhibins A and B and activin A by enzyme linked immunosorbent assays (ELISA) during postnatal development in the rat. We show that serum inhibin A levels are less than 4 pg/ml throughout postnatal life. Serum inhibin B levels peak at 572 +/- 119 pg/ml (mean +/- se) at d 40 post partum (pp) before falling to 182 +/- 35 pg/ml in mature males. Serum activin A decreases from 294 +/- 29 pg/ml at d 6 to 132 +/- 27 pg/ml at maturity. Within the testis, inhibin A levels fall from 0.330 +/- 0.108 ng/g at d 15 to less than 0.004 ng/g at maturity. Inhibin B levels peak at 43.9 +/- 4.2 ng/g at d 6 before falling to 1.6 +/- 0.13 ng/g at maturity. Testicular activin A levels fall from 18.6 +/- 2.2 ng/g at d 6 to 0.094 +/- 0.013 ng/g at maturity. Northern profiles of testicular inhibin/activin subunits correlate with immunoreactive levels demonstrated by ELISA. In situ hybridization suggests that beta(A) and beta(B) subunit expression is largely restricted to the seminiferous tubule, particularly Sertoli cells, spermatogonia, and primary spermatocytes. These data support the view that inhibin B is the major inhibin in the male rat and that levels relate to Sertoli cell number and activity. Furthermore, the demonstration of high local concentrations of activin A during the period of Sertoli cell proliferation and the onset of spermatogenesis support its proposed role because a modulator of testicular development and function.     

Altered serum profile of inhibin B, Pro-alphaC and anti-Müllerian hormone in prepubertal and pubertal boys with varicocele

OBJECTIVE: Anti-Müllerian hormone (AMH) and inhibin B are reliable markers of Sertoli cell function. The aim of the present study was to assess the functional state of Sertoli cells in order to detect early changes in the testicular function of prepubertal and pubertal patients with untreated grade II or III varicocele. DESIGN AND PATIENTS: Seven prepubertal and 55 pubertal boys with untreated grade II or III varicocele were studied. Seven prepubertal and 43 pubertal normal boys were considered as controls. MEASUREMENTS: Serum levels of gonadotrophins, testosterone, inhibin B and Pro-alphaC and AMH were determined by time-resolved immunofluorometric assays, radioimmunoassay (RIA) and specific enzyme-linked immunosorbent assays (ELISAs), respectively. RESULTS: Inhibin B and Pro-alphaC serum levels were higher in prepubertal patients with varicocele than in controls (P < 0.001). No further increment in inhibin B and Pro-alphaC levels was observed in pubertal patients with varicocele. Higher levels of AMH were found in patients in Tanner stages I, III, IV and V when compared to normal boys by Tanner stage (P < 0.05, P < 0.01, P < 0.01, P < 0.001, respectively). The direct correlation found in normal boys between inhibin B levels and LH, testosterone and testicular volume was not observed in patients with varicocele. CONCLUSIONS: The altered serum profile of gonadal hormones observed in untreated prepubertal and pubertal patients with varicocele may indicate an early abnormal regulation of the seminiferous epithelium function.     

Serum inhibin B,FSH, LH and testosterone levels before and after human chorionic gonadotropin stimulation in prepubertal boys with cryptorchidism

BACKGROUND: Several studies have indicated that cryptorchidism is associated with degenerative changes in both Sertoli cells and germ cells. The gonadal peptide hormone inhibin B reflects Sertoli cell function. Low inhibin B levels are found in a large portion of formerly cryptorchid men who show compromised seminiferous tubule function. It is not known if inhibin B can be used to demonstrate early damage of seminiferous tubules in prepubertal boys with cryptorchidism. METHODS: We investigated the relationship between serum levels of inhibin B, testosterone, FSH and LH in 62 prepubertal boys with uni- and bilateral cryptorchidism. Furthermore, we investigated the changes in serum levels of inhibin B and the corresponding changes in serum levels of FSH, LH and testosterone during a short course (3 weeks) of human chorionic gonadotropin (hCG) injections in 18 of these cryptorchid boys. RESULTS: In the 62 prepubertal boys with uni- or bilateral cryptorchidism there were no significant differences in baseline levels (median and range) of inhibin B (88 (20-195) pg/ml vs 78 (35-182) pg/ml; not significant), LH (0.08 (<0.05-0.99) IU/l vs 0.06 (<0.05-1.61) IU/l; not significant) and FSH (0.60 (0.08-3.73) IU/l vs 0.85 (0.25-2.55); not significant) compared with 156 healthy prepubertal boys, and there were no differences in hormonal levels between boys with uni- or bilateral cryptorchidism. There was no correlation between baseline levels of inhibin B and FSH. In boys younger than 9 years, we found no correlation between baseline levels of inhibin B and LH whereas, in boys older than 9 years, baseline levels of inhibin B were positively correlated to baseline LH (Spearman rank correlation coefficient ((R(s))=0.58, P=0.03). Treatment with hCG (1500 IU intramuscularly twice weekly for 3 weeks) resulted in descensus of testes in 9 out of 18 patients. In all boys but one, irrespective of age, hCG induced a marked increase in testosterone into the adult range (from undetectable to 21.8 (7.0-35.4) nmol/l; P<0.001) and completely suppressed FSH and LH levels. Serum levels of inhibin B increased significantly from 116 (50-195) pg/ml to 147 (94-248) pg/ml (P<0.05), but not uniformly. The increase in serum levels of inhibin B was inversely correlated to baseline inhibin B (Rs=-0.52, P=0.03) and baseline FSH (R(s)=-0.59, P<0.01). CONCLUSIONS: We therefore suggest that, in the prepubertal testes, inhibin B is secreted from the prepubertal Sertoli cells following hCG, whereas early pubertal testes with more differentiated Sertoli cells are not able to secrete inhibin B in response to hCG stimulation, perhaps due to lack of germ cell-derived betaB-subunits. We found (a) normal inhibin B levels in prepubertal boys with uni- or bilateral cryptorchidism, (b) that hCG stimulated testosterone markedly and suppressed FSH and LH levels and (c) that hCG treatment stimulated inhibin B levels in the youngest cryptorchid boys. In the oldest prepubertal boys no hCG-induced changes in inhibin B were shown.     

Inhibin B levels in azoospermic subjects with cytologically characterized testicular pathology

BACKGROUND AND OBJECTIVE: Inhibin B, a heterodimeric glycoprotein of gonadal origin, is the most important circulating form of inhibin in human males and an inverse relationship between inhibin B and FSH plasma levels was been recently observed. Azoospermia represents the end-point of different kinds of testicular damage, ranging from a normal spermatogenic pattern (obstructive forms) to the complete absence of germ cells (Sertoli Cell Only Syndrome, SCOS). Furthermore, azoospermia may be related to maturational disturbances at different levels (spermatogonial, spermatocytic, spermatidic). To better define the relationship between testicular damage and inhibin levels and to evaluate the diagnostic value of this hormone in the management of subjects with azoospermia, we performed specific inhibin B assays in a group of azoospermic subjects affected by different kinds of testicular pathology. PATIENTS: Eighty-nine azoospermic men were studied by testicular ultrasound examination, fine needle aspiration of the testes and hormonal parameters (FSH, LH and testosterone, inhibin B). Thirty normozoospermic subjects were considered as controls for seminal and hormonal parameters. DESIGN AND RESULTS: On the basis of cytological analysis five different testicular appearences were identified in azoospermic patients: (i) Sertoli cell only syndrome (SCOS); (ii) Severe hypospermatogenesis; (iii) Spermatogonial and/or spermatocytic arrest; (iv) Spermatidic arrest; (v) Normal germ line (obstructive forms). No difference in LH and testosterone levels was found among the different groups. A significant negative correlation was present between inhibin B and FSH both in azoospermic men (r = - 0.503, P < 0.0001) and normozoospermic controls (r = -0.361, P < 0.05). Groups characterized by obstructive azoospermia and spermatidic arrest showed inhibin B concentrations similar to normozoospermic subjects (130.7 +/- 73.5, 160.3 +/- 35.1 and 148.5 +/- 46.8 ng/l, respectively), while groups characterized by SCOS, severe hypospermatogenesis and spermatogonial and/or spermatocytic arrest showed mean inhibin B concentrations significantly lower than controls (56.5 +/- 56.0, 57.9 +/- 31.2; 48.9 +/- 16.7 ng/l, respectively). In the group of SCOS, 8 out of 42 subjects (19.0%) showed inhibin B concentrations within the normal range despite high FSH levels. CONCLUSIONS: This study demonstrated that, in humans, spermatids play an important role in the mechanism regulating inhibin B secretion by Sertoli cells. The significance of this hormone as a diagnostic parameter in azoospermic patients does not seem to be specific because it does not permit discrimination between obstructive forms or spermatidic arrest. Furthermore, despite an evident clinical, cytological and hormonal pattern for SCOS, inhibin B levels are normal in some of these patients. The significance of this latter result remains to be elucidated.     

Correlation between inhibin secretion and damage of seminiferous tubules in a model of experimental autoimmune orchitis.

The aim of the present study was to evaluate inhibin secretion in rats with autoimmune orchitis. As we have previously described, experimental autoimmune orchitis (EAO) induced in rats by active immunization with testis homogenate and adjuvants is characterized by an interstitial mononuclear cell infiltrate and sloughing of the germinal epithelium. At 120 days after the first immunization 60% of the rats exhibited a severe orchitis with large areas of aspermatogenic seminiferous tubules in which only spermatogonia and Sertoli cells with cytoplasmic vacuolization remained attached to the tubular wall. None of the untreated (N) or control (C) rats revealed pathological alterations. Sixty percent decrease in testis weight was observed in rats with EAO compared with N or C groups. A 3-fold increase in serum FSH levels was observed in rats with EAO compared with N or C groups (19.8+/-3.7 vs 5.6+/-0.3 and 5.9+/-0.1 ng/ml respectively). A significant decrease in inhibin B levels was observed in rats with EAO when compared with N or C groups (40+/-4.6 vs 207+/-38.8 and 221.4+/-28.6 pg/ml respectively). An inverse correlation between inhibin B and FSH serum levels and a direct correlation between inhibin B and testis weight were found. Strong expression of the inhibin alpha-subunit in Sertoli cells of untreated and control rats was observed; this subunit was undetectable or poorly detectable in rats with orchitis. Positive staining for the inhibin alpha-subunit was also observed in Leydig cells of all groups studied. In conclusion, using a model of autoimmune orchitis our results show that circulating inhibin B levels and inhibin alpha-subunit expression in Sertoli cell cytoplasm closely correlate with the degree of damage of the germinal epithelium.     

Testicular volume in relation to hormonal indices of gonadal function in community-dwelling elderly men

Aging is accompanied by involutional changes in testicular function; limited data suggest a decrease in bilateral testicular volume (BTV). We studied BTV by ultrasonography in relation to serum gonadal hormones in 115 healthy elderly men (median age, 78 yr) and 42 young men (median age, 26.5 yr). Elderly men had a clearly smaller BTV (mean, 20.6 vs. 29.7 ml; P < 0.001), whereas serum inhibin B was slightly but significantly decreased (mean, 176.8 vs. 212.8 ng/liter; P = 0.04); lower values in the elderly were observed for bioavailable (Bio) testosterone (T), Bio 17 beta-estradiol, inhibin B/FSH (mean, 18 vs. 58 ng/mU; P < 0.001), and T/LH ratios. In the elderly and the young, respectively, BTV was associated with inhibin B (r = 0.53, P < 0.001; r = 0.41, P < 0.01), FSH (r = -0.53, P < 0.001; r = -0.48, P < 0.01), and inhibin B/FSH ratio. Only in the old men was BTV significantly associated with LH (r = -0.32; P < 0.001), Bio T (r = 0.26; P < 0.01), and T/LH (r = 0.48; P < 0.001). In a multivariate analysis, FSH, inhibin B, and Bio T were independently associated with BTV in the elderly (R(2) = 0.34). Receiver operating characteristics curve analysis indicated that BTV at a criterion value of 14.3 ml had a sensitivity of 46% and a specificity of 79% to predict low serum Bio T levels in the elderly. In conclusion, the moderately decreased BTV observed in elderly men, strongly associated with a decrease of the inhibin B/FSH ratio, is consistent with a reduced Sertoli cell mass, compensated by increased FSH stimulation resulting in only limited decrease of Sertoli cell function. Finding of a low testicular volume in elderly men can contribute to the diagnosis of hypogonadism, but this criterion has low sensitivity to detect decreased T production.     

Regulation of FSH beta messenger ribonucleic acid levels in the rat by endogenous inhibin.

This study investigated the role of endogenous inhibin in regulating FSH beta mRNA levels subsequent to the gonadotropin surge in the immature, estradiol (E2)-treated female rat. Rats which undergo FSH surges on day 29 have low to undetectable levels of FSH beta mRNA at 0900 h on day 30, whereas those treated simultaneously with E2 and progesterone (P) implants to block these surges have considerably higher levels of FSH beta mRNA. In view of the profound inhibitory effect of inhibin on FSH beta mRNA, we examined the possibility that increased inhibin secretion is responsible for the decline in FSH beta mRNA levels on the morning after the FSH surge by immunoneutralization of endogenous inhibin. Twenty-eight day-old rats which received E2 and blank (B1) or P implants were injected iv with 0.4 ml of a potent anti-rat inhibin serum (anti I alpha, prepared in sheep against rat inhibin alpha (1-26)-Tyr27 coupled to human alpha-globulins) or normal sheep serum at 1700 to 1830 h on day 29 and were killed at 0900 h on day 30. Animals which received the inhibin antiserum showed significantly (P less than 0.001) elevated serum FSH levels (22.9 +/- 1.9 ng/ml [E2 + B1] and 17.1 +/- 0.6 ng/ml [E2 + P]) compared to those which received normal serum (4.4 +/- 0.1 [E2 + B1] and 4.2 +/- 0.1 [E2 + P]). Serum LH was undetectable (less than 0.6 ng/ml) in all groups. Free glycoprotein alpha-subunit was also increased (P less than 0.001) by antiserum to inhibin in E2 + B1-treated rats but was significantly suppressed by P after injection of either normal serum or anti I alpha. Total pituitary RNA was extracted and hybridized to cDNA probes for rat FSH beta, LH beta, and the common alpha-subunit by Northern blot analysis; RNA levels were normalized with beta-actin or cyclophilin probes. As expected, in rats which received normal serum, FSH beta mRNA levels were about 4-fold higher after treatment with E2 + P implants than after treatment with E2 + B1 implants. However, injection with anti-inhibin serum resulted in a striking elevation of FSH beta mRNA levels: 13-fold in animals treated with E2 + B1 implants and 5-fold in animals treated with E2 + P implants. There were no significant differences in levels of LH beta or alpha-subunit mRNAs between rats which received anti-inhibin or normal serum although there was a 30-40% decrease in alpha mRNA after P treatment.(ABSTRACT TRUNCATED AT 400 WORDS)     

Lack of evidence of a genetic origin in the impaired spermatogenesis of a patient cohort with low-grade varicocele

Varicocele is the most common clinical finding in infertile men but controversy continues to surround the utility of its treatment. An increased response of FSH to gonadotrophin-releasing hormone testing has been described in patients with varicocele, while the co-influence of Yq chromosome microdeletions in the infertility associated to this pathology is still under investigation. We studied 30 patients with first- and second-grade varicocele, 15 idiopathic oligozoospermic men and 21 age-matched healthy controls. All subjects underwent testicular Doppler ultrasonography, semen analysis, gonadotrophin-releasing hormone testing and baseline blood sampling for total and free testosterone, PRL, 17beta-estradiol, SHBG evaluation and Yq chromosome analysis. Apart from FSH, no difference in baseline hormonal levels was found between the groups. The patients with varicocele showed both an increased basal (p=0.007) and GnRH-induced FSH response (peak and AUC) (p=0.004) in comparison with the controls, while the idiopathic oligozoospermic men had only higher GnRH-induced FSH AUC (p=0.04). In the varicocele group, FSH peaks after GnRH testing correlated positively with the grade of disease (r=0.42, p=0.02) and negatively with sperm count (r=-0.50, p=0.005) and bilateral testis volume (r=-0.52, p=0.005). Sperm count and sperm motility were similarly significantly reduced both in patients with varicocele and in patients with idiopathic oligozoospermia in comparison with healthy controls. Yq chromosome analysis by sequence-tagged site PCR revealed no microdeletion in the AZF regions in any subject studied. Given the quite small number of subjects studied, our overall findings can only prompt us to suggest a possible causal role of varicocele in the impairment of spermatogenesis in our patients. Furthermore, although a genetic co-influence (i.e. Yq microdeletions) does not seem to be involved in the pathogenesis of infertility in men with varicocele and mild to moderate oligozoospermia, genetic screening seems to be advisable, especially in those patients who present a severe impairment of sperm count, as has been suggested by recent literature data.